The study examined the distance between the homes of pregnant women and freeways, highways and main roads. It counted the number of roads around the homes in radii of 50 to 500 metres to determine at what distance negative effects on birth outcomes might occur. Most of the effects were within a 200-metre radius, but negative health effects were present up to 400 metres.

The results showed no statistically significant effect on birth times for those mothers living close to just one freeway, highway or main road. There was an effect when mothers lived close to a number of main roads. The study found that for every 10 extra main roads within 400 metres of the home, gestation time was reduced by 1.1%.

In a QUT media release, lead researcher, Associate Professor Adrian Barnett, says that the more freeways and highways around a pregnant woman's home, the higher the likelihood of her baby being born prematurely. He said, "The most striking result was the reduction in gestation time of 4.4 per cent or almost two weeks associated with an increase in freeways within 400 metres of the women's home."

Freeway Stack

Justin Cozart

Associate Professor Barnett does caution that the increased risks are relatively small. However, he adds that this still has large public health implications because, "pre-term and low-birth weight babies stay in hospital longer after birth, have an increased risk of death and are more likely to develop disabilities."

The study does not clearly determine the reasons for the early births but points to both noise and air pollution as possible contributing factors. "My feeling is that it's more likely to be the toxins in the air pollution, but we can't definitively rule out noise yet," said Associate Professor Barnett in an ABC Report.

Associate Professor Peter Franklin of the School of Population Health at the University of Western Australia, says this study is the latest in a growing swathe of evidence that pollution damages the health of children. He said, “The increasing evidence, including the current study, needs to be considered by city and town planners as they design road networks and housing developments to cater for our growing population.”